1. Field of the Invention
This invention relates to a logic synthesis apparatus for composing a logic circuit to be designed based on a functional specification of the logic circuit, and particularly to a logic synthesis circuit having an automatic learning function for incorporating an additional transformation rule in a group of conversion rules given in advance to the apparatus without causing competition to the group of conversion rules.
2. Description of the Prior Art
With the improvement of the integrating technology, LSI logic circuits become more large-scale and complicated. Therefore, the design work for the circuits becomes more complex and requires much more time. Accordingly, there is a proposition to provide a logic synthesis apparatus having a group of conversion rules as a knowledge base for producing a logic circuit with a function when a functional specification for representing the function is inputted, so as to enable automatically composing a logic circuit only by inputting the functional specification. By using this apparatus, it is attempted to easily design a logic circuit and reduce the design time.
In such a logic synthesis apparatus, the group of conversion rules as a knowledge base is composed of conversion rules required for producing a logic circuit in accordance with a functional specification. The group of conversion rules is obtained by expressing a method ordinarily used for designing logic circuits by producing a logic circuit from a functional specification as conversion rules, and gathering the conversion rules into a group. To make the logic synthesis apparatus applicable to the designers in common as widely as possible, the number of the conversion rules to be incorporated in the apparatus is minimized as far as the logic design is possible. Accordingly, by this apparatus, even when the designers are different, the same logic circuit can be obtained as far as the functional specification is the same. However, because of difference in design approaches by designers, even when the functional specification is the same, the logic circuits to be realized by them are occasionally different. Therefore, even though it is attempted to design the same logic circuit, the difference caused by respective designing approach of designers must be examined in detail. However, it is very difficult and troublesome to minutely discriminate the difference.
While, composing a logic circuit designed along each designing approach of designers, it is necessary to add a transformation rule original for the designer to the group of conversion rules as a knowledge base. However, in this case, it is necessary to consider the coordination or matching property between the additional transformation rule and the group of conversion rules given in advance. Namely, when the additional transformation rule is added to the knowledge base, the additional rule must be incorporated therein after the group of conversion rules is revised so as to avoid the competition between the additional rule and the group of conversion rules. Accordingly, the designer must examine the function of the group of conversion rules given in advance, and revise it along the above object, further add the additional transformation rule thereto. As the result, it becomes very troublesome for the designer, particularly for one who is not an expert of the knowledge base design, to do this work.
As mentioned above, when a logic circuit designed along each designing way of circuit designers is composed by the conventional logic synthesis apparatus, the designer must take extremely much trouble to carry out the addition or alteration to the knowledge base.